Cor Triatriatum Sinister Presenting with Severe Pulmonary Venous Obstruction and Cardiogenic Shock in a Three-Month-Old Infant: A Case Report
Fjorba Mana *1, Ketjon Menkshi 2, Arben Baboci 1, Saimir Kuci 3, Alfred Ibrahimi 3, Marsela Goga 3, Numila Kuneshka 4, Albert Koja 4, Altin Veshti1
*Correspondence to: Fjorba Mana, Service of Cardiac Surgery, University Hospital Center “Mother Theresa,” Tirana, Albania.
© 2026 Fjorba Mana. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received: 25 February 2026
Published: 01 August 2026
DOI: https://doi.org/10.5281/zenodo.21714934
Abstract
Background: Cor triatriatum sinister (CTS) is an uncommon congenital cardiac anomaly characterized by a fibromuscular membrane subdividing the left atrium. Clinical severity varies, with symptomatic restriction leading to pulmonary venous hypertension and congestive manifestations.
Case Presentation: We describe a three-month-old infant presenting with respiratory distress, feed intolerance, hepatomegaly, and signs of cardiogenic compromise. Transthoracic echocardiography revealed a restrictive supramitral membranous partition with a 4 mm opening, resulting in severe pulmonary venous obstruction and hemodynamic instability. Urgent surgical resection of the membrane under cardiopulmonary bypass resulted in complete anatomical and functional relief. The postoperative course was uneventful, with normalization of hemodynamics and growth trajectory.
Conclusion: CTS can present emergently in infancy with symptoms similar to obstructive left heart lesions. Echocardiography is critical for diagnosis. Prompt surgical intervention results in excellent outcomes. This case highlights the need for heightened clinical suspicion and early surgical referral.
Keywords: Cor triatriatum sinister; congenital heart disease; supramitral membrane; cardiogenic shock; cardiac surgery.
Introduction
Cor triatriatum is a rare congenital cardiac anomaly in which a fibromuscular membrane divides the atrium into two chambers. It most commonly affects the left atrium (cor triatriatum sinister) and accounts for less than 0.1% of clinically diagnosed congenital heart diseases. Although it may present as an isolated defect, it is frequently associated with other congenital cardiac anomalies.
In cor triatriatum sinister (CTS), the left atrium is divided into a posterior chamber receiving pulmonary venous return and an anterior chamber that communicates with the mitral valve. The degree of obstruction depends on the size of the membrane fenestration. Severe restriction may lead to pulmonary venous hypertension, right-sided pressure overload, congestive heart failure, and in rare cases, cardiogenic shock in early infancy.
We present a case of isolated CTS in a three-month-old infant who developed severe hemodynamic compromise requiring urgent surgical intervention.
Case Presentation
A three-month-old infant was brought to the emergency department with pallor, recurrent episodes of apnea, and grunting respirations. The parents reported progressive feeding intolerance and poor weight gain over several weeks.
On admission, the infant was in critical condition. Clinical examination revealed tachypnea, subcostal retractions, poor peripheral perfusion, hepatomegaly consistent with hepatic congestion, and signs of pulmonary congestion. Oxygen saturation was reduced, and the patient demonstrated compromised hemodynamic parameters requiring immediate stabilization and initiation of inotropic support.
Chest radiography showed pulmonary vascular congestion. Laboratory findings were consistent with systemic hypoperfusion.
Transthoracic echocardiography revealed a supramitral fibromuscular membrane dividing the left atrium into two chambers. The posterior chamber received all pulmonary veins, while the anterior chamber communicated with the mitral valve. A restrictive orifice measuring approximately 4 mm was identified, generating significant flow acceleration and a functional picture mimicking severe mitral stenosis. Elevated pulmonary pressures and right ventricular strain were noted. No associated congenital cardiac anomalies were identified.
Surgical Technique
Given the patient’s hemodynamic instability and echocardiographic severity, urgent surgical intervention was planned.
Under general anesthesia and median sternotomy, cardiopulmonary bypass (CPB) was instituted with moderate hypothermia (31°C). Myocardial protection was achieved using antegrade cardioplegia. A right atriotomy was performed with access to the left atrium across a small secundum ASD to optimize visualization.
Intraoperative inspection confirmed a thick fibromuscular membrane located just above the mitral valve orifice, creating a restrictive partition. All four pulmonary veins were visualized draining into the posterior chamber. The membrane was completely excised, ensuring unobstructed pulmonary venous drainage and maintaining the integrity of the mitral valve apparatus.
The heart was de-aired, and the patient was successfully weaned from CPB with stable hemodynamics.
Postoperative Course
Postoperatively, the infant showed progressive hemodynamic stabilization. Inotropic support was gradually tapered. Follow-up echocardiography demonstrated complete removal of the membrane, no residual obstruction, normal pulmonary venous drainage, and preserved mitral valve function.
The postoperative course was uneventful, and the patient was discharged in stable condition. At follow-up, growth and clinical status were appropriate for age, with no evidence of recurrence or residual obstruction.
Discussion
Cor triatriatum sinister is an uncommon congenital anomaly first described anatomically by Church and later named by Borst. The anomalous partition within the left atrium may impede pulmonary venous return depending on fenestration size. Historically, cases with large fenestrations are asymptomatic until later in life, while infants with restrictive orifices present early with significant morbidity.
Epidemiology and Embryology
Although rare, reported incidence in congenital heart disease registries suggests approximately 0.1–0.4%. Embryologically, it is hypothesized to result from failure of common pulmonary vein incorporation into the left atrium during cardiac development, leading to persistent membranes.
Clinical Presentation
Infants with severe obstruction often present within the first months of life. Respiratory symptoms, tachypnea, feeding intolerance, hepatomegaly, and failure to thrive mirror left-sided obstructive lesions and may be misdiagnosed as primary pulmonary disease. In our case, the severity of restriction and resultant pulmonary venous hypertension produced a clinical picture akin to critical mitral stenosis.
Comparative studies show that CTS associated with ASD/PFO may present later with less acutely obstructive physiology, as the interatrial communication decompresses left atrial pressures. Isolated cases without septal defects, as in our patient, may therefore present more severely.
Diagnostic Modalities
Echocardiography remains the primary diagnostic modality, allowing dynamic assessment of membrane morphology, fenestration size, gradients, and secondary effects on right heart pressures. Roldán et al. reported 3-D echocardiography provides comprehensive visualization of membrane attachments and size, aiding surgical planning. While advanced imaging (MRI, CT) offers complementary anatomical detail, its use is limited in unstable infants.
Differential diagnoses include supravalvar mitral ring, mitral stenosis, and pulmonary venous anomalies. The supramitral membrane in CTS is distinguished by its location and characteristic flow patterns on Doppler.
Surgical Management and Outcomes
Surgical excision of the membrane is definitive. Timing is dictated by symptom severity. Elective repair in asymptomatic individuals with mild gradients may be considered; however, urgent intervention is indicated for those with hemodynamic compromise. Early surgical reports by Lewis and colleagues demonstrated the feasibility and effectiveness of membrane resection, and multiple series since have confirmed low operative mortality with complete excision.
Long-term outcomes are favorable. Freedom from reintervention is high when complete excision is achieved initially. Postoperative pulmonary vascular remodeling occurs gradually, with normalization of pressures over weeks to months.
Literature Comparison
A review of indexed case series highlights that:
In a multicenter series of 50 patients published in Pediatric Cardiology, isolated CTS represented approximately 20% of cases, with excellent survival at 1 and 5 years (>95%). Another analysis in Annals of Thoracic Surgery corroborated that urgent surgical resection in symptomatic infants leads to low morbidity and excellent functional outcomes.
Clinical Implications
This case reinforces the necessity for high clinical suspicion in infants with unexplained respiratory distress and signs of pulmonary venous hypertension. Early echocardiography expedites diagnosis, and prompt surgical referral prevents progression to irreversible pulmonary vascular changes.
Conclusion
This case highlights the importance of early recognition of cor triatriatum sinister in infants presenting with respiratory distress and hemodynamic instability. Echocardiography plays a crucial role in establishing the diagnosis. When severe obstruction is present, urgent surgical correction results in rapid clinical improvement and excellent long-term outcomes.
References